The present invention relates to a cutting apparatus for use in a cutting machine, and to a block for use in a cutting apparatus.
Cutting machines are used in a variety of applications including mining, digging and earth working operations. One application of a cutting machine in the removal of asphalt surfaces from roads. The cutting apparatus of a cutting machine is coupled to a drive mechanism which drives or otherwise rotates the cutting apparatus.
A known cutting apparatus of the prior art includes a cutting drum which is commonly, although by no means exclusively, generally cylindrical in shape. The cutting apparatus has disposed about its surface a number of cutting assemblies comprising a cutting tool mounted in a holder. The cutting tool assemblies are welded, bolted or otherwise attached to the radially outer surface of mounting blocks which extend from the cutting drum. These bulky mounting block and cutting tool assemblies are staggered about the surface of the drum.
When operating the cutting machine, the projecting portions of the cutting apparatus including the cutting tool assemblies hit various parts of the material being removed or excavated. In the particular application of a cutting machine used to remove a road surface, there are hidden obstructions under the surface of the road that are hit by the cutting machine including sewer drains, manhole pits, stormwater covers, steel bars including train and tram tracks, and water mains shut-off valves. When various portions of the machinery hit particularly hard obstructions, various parts of the cutting apparatus break away. The holder is usually the weakest point of the cutting apparatus, and accordingly the holders are commonly broken and must be replaced. In addition, a great deal of strain is placed on the drive mechanism as the bulky parts of the cutting apparatus strike these obstructions, sometimes preventing the cutting apparatus from rotating.
Taking a cutting machine out of operation for repair of the cutting apparatus is a very costly exercise. One expensive cost component associated with repairing the cutting machine is the loss of potential revenue which cannot be obtained while the cutting machine is out of operation.
Various techniques have been developed in order to simplify the replacement of holders on a cutting apparatus in a cutting machine. One method involves the use of a holder having a T-shaped shank which can be slidably inserted into a base portion which is welded directly onto the mounting block. When the holder breaks away, any remaining portion of the holder can be slid out of the base a new holder can be reinserted. This does to some extent reduce the amount of time taken to repair the cutting apparatus.
Another problem associated with known cutting apparatus is that as the cutting apparatus is rotated, the various bulky protruding sections of the apparatus come into contact with the surface being worked a cause considerable stress on the drive mechanism which drives the cutting apparatus. Repairing the drive mechanism can be costly and time consuming.
It is accordingly desirable to provide a cutting apparatus which is relatively simple to repair to minimise the time during which the cutting machine is out of operation.
According to the present invention there is provided a cutting apparatus which includes:
a rotatable member having an outer surface; and
a plurality of cutting tool assemblies, each assembly including a cutting tool mounted in a holder,
wherein the cutting tool assemblies are mounted on the rotatable member so that the holder is shielded by the rotatable member and the cutting tool extends beyond the outer surface of the rotatable member a sufficient distance to operate as a cutter.
As is well known in the art of the invention, holders are usually used for receiving cutting tools because the cutting tools generally need to be received in a region of high-strength (and therefore higher quality and more expensive) metal. It is generally cheaper to provide a separate holder of high-strength material, rather than an entire rotatable member made from high strength material. However, it is possible for the holder to be integral with the rotatable member. In this case, the rotatable member could be made entirely from the high-strength steel, and a region of this member which receives and supports the cutting tool constitutes the holder of the cutting tool assembly.
By providing a rotatable member which shields the holder of the cutting tool assembly the problem associated with breaking cutting holders is avoided. In particular, when only the cutting tool extends beyond the outer surface of the rotatable member, only the cutting tool is subjected to forces which may result in breakage. The cutting tool can be simply and inexpensively replaced by removal of any broken portion of the cutting tool and replacement with a new cutting tool.
It is less expensive to replace a cutting tool than the entire holder or block of the rotatable member of the prior art. The cutting tool is approximately eight times less expensive than the holder. In addition, according to a preferred embodiment, the cutting tool is merely seated with a retaining clip in the holder and is not bolted, welded or otherwise affixed rigidly thereto. It takes much less time to replace the cutting tool than it does to replace the entire cutting tool assembly or block. In the prior art, when the holder or block breaks, this must be re-welded or bolted onto the mounting block. This takes much more time, and often cannot be done on site.
Preferably, the shielding is provided in a region to the side of and/or in front of the holder in the direction of rotation of the rotatable member. The shielding may be provided in a region diagonally in front and to the side of the holder, in the direction of rotation of the rotational member.
Preferably, the portion of the rotatable member defining the outer surface of the rotatable member shields the holder.
It is preferred that the outer surface of the rotatable member be substantially continuous in the sense that any breaks or crevices in the outer surface are not so large or are not located so as to cause stress on the mechanism driving the rotatable member. The idea behind this is that the rotating outer surface of the rotatable element should ride relatively smoothly over the surface being removed, with only the cutting teeth extending beyond the outer surface and into the material being cut. Accordingly, it may be possible for there to be small breaks or irregularities in the outer surface, provided that the arrangement of these breaks is not much as to alter the relatively smooth rotation of the outer surface over the surface being cut. Accordingly, it is a preferred feature of the invention that the outer surface of the rotatable member be shaped to enable the rotatable member to maintain continuous contact with the surface being cut as it rotates in a cutting operation. More preferably, the rotatable member maintains smooth continuous contact with the surface being cut during the cutting operation.
The object of this embodiment is to ensure that the teeth do the work in cutting the surface being cut, and not any irregular or protruding parts of the cutting apparatus. This also ensures that the rotational driving force is primarily transferred into cutting force as exposed to stress forces arising from irregular contact with the surface being cut.
It is particularly advantageous to provide smooth continuous contact between the rotatable member and the surface being cut, since this substantially reduces the impact loading on the drive mechanism for the rotating cutting apparatus, and ensures that the cutting tools principally do the cutting work, and are subjected to the stress of striking the surface being cut. In one commonly known cutting apparatus, the bulky mounting block and cutting tool assemblies are unevenly randomly distributed about the surface of the rotatable drum. This results in irregular impact and strain being applied to the drive mechanism an to the cutting apparatus itself.
It is particularly preferred that the outer surface of the cutting apparatus forms a spiral or helix. For example, the outer surface of the cutting apparatus may be in the form of two helices which start at the outer edges of the rotatable member and wind inwardly towards the centre of the rotatable member. Other various arrangements are also possible. For example, the outer surface may include a number of interposed or meshing spirals or helices. The spiral(s) or helix (helices) may have a constant or varying angle of intersection to the axis of the rotatable member.
It has been explained above that it is preferred that the outer surface of the rotatable member be shaped to ensure that the rotatable member maintains continuous (and smooth) contact with the surface being cut as it rotates in a cutting operation. In the situation where the outer surface is generally spiral or helical, this may be brought into effect by having a continuous outer surface of constant radius (for generally cylindrical rotatable members) or smoothly increasing radius (for generally conical or xe2x80x9cpineapple-shapedxe2x80x9d rotatable members).
It is possible for the cutting tools in this situation to be located to one side of the helix or to be recessed into the helix in alignment with the helix. When the cutting tools are in line with the helix (thereby forming a small break in the outer surface), it is still possible for the rotatable member to maintain continuous and smooth contact with the surface being cut. This is achieved by having a sufficient number of sections of the outer surface extending laterally across (eg. when cylindrical) or around (eg. when conical) the rotatable member having a uniform radius. There should be enough of these sections laterally in line with one another to compensate for any broken sections in the same lateral plane to enable the rotatable member to maintain continuous a smooth contact with the surface being cut.
Preferably the cutting tools are evenly distributed about the surface of the cutting apparatus.
Preferably the rotatable element comprises a rotatable drum and a housing mounted to the drum, wherein the outer surface of the housing forms the outer surface of the rotatable element. Accordingly, in one form of the invention, the rotatable member is in the form of a drum having a helical upstanding ridge. The drum may of of any suitable shape, including cylindrical, conical and xe2x80x9cpineapplexe2x80x9d shapes.
When the drum is cylindrical, it is preferred that the radial distance from the axis of the rotatable drum to the outer surface of the housing is substantially constant along the length of the rotatable drum. It is not necessary for the radial distance to be absolutely constant. For example, there may be a small variations or irregularities in this radial distance. It is envisaged however that the variation in the radial distance will not be so substantial as to provide such an irregular surface that there will be irregular and unbalanced contact between the housing and the surface being cut.
Preferably the housing of the cutting apparatus has a side surface that is substantially constant (even). The provision of the substantial constant side surface for the housing facilitates removal of the cut material through the helical spiral of the cutting apparatus and with minimum resistance or drag caused by any uneven surfaces. This streamlining of the side surfaces has been found by the applicant to improve the operating efficiency of the cutting apparatus.
Preferably the housing includes a series of blocks, each bearing one of the cutting tool assemblies. Preferably, each block constitutes a segment of a ring.
Preferably the holder is seated within an aperture in the rotatable element.
Preferably the holder includes a channel which receives a shalt of the cutting tool to enable mounting of cutting tool in the holder.
Preferably the aperture in which the holder is seated is aligned with the channel in the holder.
Preferably the rotatable body includes a cavity located at an inner end of the aperture that opens to the aperture and, in use, when a cutting tool breaks at the shaft, the shaft of a cutting tool can either:
pass through the channel of the holder, through the aperture seating the holder and into said cavity, so that the shaft of a new cutting tool can be received in the holder, or
be pressed through the aperture and away from the cavity for removal and replacement with a new cutting tool.
According to the present invention there is also provided a cutting apparatus which includes.
a rotatable member having a helical housing and an outer surface and
a plurality of receiving means for receiving shafts of cutting tools,
wherein, in use, cutting tools are mounted via their shafts in the receiving means so that the receiving means are shielded by the portion of the helical housing defining the outer surface, and wherein, in use, the rotating outer surface of the helical housing rides over the surface being removed with the cutting tools extending radially beyond the outer surface a sufficient distance to operate as cutters so that cutting force is applied to the surface being cut by the cutting tools and not the outer surface of the helical housing.
According to the present invention there is also provided a cutting apparatus including a rotatable member having a helical upstanding ridge, an outer face and apertures for receiving and seating cutting tools disposed about the helical upstanding ridge, the cutting tools each including a shaft and a tip, and the apertures being arranged so that cutting tools located in the apertures are positioned with tips of the cutting tools project radially outwardly of the outer face,
wherein the helical upstanding ridge includes cavities opening to the apertures, so that, in use, when a cutting tool breaks at the shaft, the shaft of the cutting tool can either pass radially inwardly through the aperture and into said cavity, or can be pressed radially outwardly utilising access via the cavity, so that the shaft of a new cutting tool can be received in the holder.
Preferably, the apertures are formed in radially recessed regions of the helical upstanding ridge.
According to the present invention there is also provided a block for use on a cutting apparatus including a rotatable body and an outer surface, said block including:
a first surface for forming the outer surface of the cutting apparatus; and
a receiving means for receiving a cutting tool assembly which comprises a cutting tool mounted in a holder,
wherein the receiving means is positioned so that, in use, a holder located in the receiving means will be shielded by the first surface of the block, and the cutting tool will extend beyond the first surface of the block a sufficient distance to operate as a cutter.
As explained above with reference to the cutting apparatus, the holder may be separate to, or integral with the block.
A plurality of like blocks maybe mounted either directly or indirectly onto a rotatable drum to form a cutting apparatus having shielded holders.
Preferably the receiving means is recessed from the first surface of the block. Preferably, the receiving means is positioned to one side of the first surface of the block. Preferably the first surface of the block is arcuate in shape.
Preferably, the block includes a second surface adapted for mounting directly or indirectly to a rotatable drum. Preferably the block includes two opposite ends which interconnect the first and second surfaces of the block.
Preferably the block is shaped so that when two like blocks are positioned one next to the other, the first surface of one block is aligned with the first surface of the second block to define a substantially continuous outer surface. Accordingly, it is particularly preferred that the block be in the shape of a segment of a ring.
Preferably the receiving means comprises an aperture, in which the cutting tool assembly can be seated.
Preferably the block includes a cavity located to one end of the aperture defining the receiving means, such that, in use, when a cutting tool breaks, a shaft of the cutting tool can either;
pass through the aperture and to the cavity to facilitate removal of the broken cutting tool and replacement with a new cutting tool, or
be pressed through the aperture away from the cavity for removal and replacement with a new cutting tool.
Preferably the block includes two opposite side walls. More preferably, the opposite side walls of the block are dimensioned so that when two like blocks are positioned one next to the other, the side walls of the adjacent blocks are substantially aligned.
According to the present invention there is also provided a block for use on a cutting apparatus including a rotatable body and an outer surface, said block including:
a first arcuate surface for forming the outer surface of the cutting apparatus; and
an aperture for receiving and seating a cutting tool assembly which comprises a cutting tool mounted in a holder, the aperture being located to one side of the first arcuate surface so that the holder will be shielded by the portion of the block defining the arcuate surface and the cutting tool will extend beyond the first arcuate surface of the block a sufficient distance to operate as a cutter.
According to the present invention there in also provided a block for use on a cutting apparatus including a rotatable body and an outer surface, said block including:
a first surface for forming the outer surface of the cutting apparatus;
a second surface opposite the first surface adapted for mounting directly or indirectly onto a rotatable drum,
a pair of opposite ends interconnecting the first and second surfaces,
a pair of opposite side walls, and
a recessed region adjacent or within the first surface, said recessed region including an aperture for receiving and seating a cutting tool assembly which comprises a cutting tool mounted in a holder, the aperture being positioned to seat the cutting tool so that the tip of the cutting tool extends outwardly beyond the first surface of the block.
According to the present invention there is also provided a method of retro-fitting a cutting apparatus including a rotatable body to provide a cutting apparatus having shielded holders or holder regions, the method including steps of:
(i) removing the outer profile of the rotatable body to obtain a stripped rotatable body; and
(ii) mounting the stripped rotatable body of step (i) with the blocks described above.
The removal of the outer profile of the rotatable body may be effected by machining the outer profile of the body to obtain a curved surface, and mounting blocks onto the machine-curved surface. Alternatively, the rotatable body of the cutting apparatus may be stripped back to the rotatable drum, and the blocks mounted directly onto the rotatable drum.